Saturday, February 17, 2007

A crucial and far-reaching feedback in global warming and subsequent climate change is the slowing down of the Atlantic thermohaline circulation colloquially known as the Gulf stream.

If the Gulf current weakens further...

When it happened before ( and it happened - according to native Americans memories) the midland drought on the American continent lasted 40 continous and relentless years. Currently we could be in about the third...

Kuro-siwa and Gulf

The two most important oceanic streams known are the Kuro-siwa in the Pacific and the Gulf Current in the North Atlantic. Both already weakened and continue to weaken. The first is getting diluted by ice melting in the Antarctic and the second - by the ice melting in the Polar Ice cap and the Greenland ice sheet.

Out of the two the Gulf may be at larger risk. In the picture below you can see streams along the coast lines. The blue and green streams are deep ocean currents carrying heavy and more salty cold water. The orange and red ones are the warm surface currents. Between the two are yellow streams.

There are many things that effect circulation, but here we'll concentrate on two. One is the heavy salt that makes cold water sink so it can remain cold while it journeys back to the Mexican Gulf. The second is the many multitudes of smaller streams around the Greenland plain that constitute mostly the cold back-flow. If there is no back flow - there is no current.

Warm surface water carries warm air above. That constant supply of warm air is responsible for the relatively mild climate of Northern Europe. The sun doesn't heat this area sufficiently, so without the Gulf circulating there would be no warm air here. The Gulf is the guardian angel of moderate climate in this region.

Imagine it slowing and slowing to the point where just the jagged edges of Greenland alone would pose a significant barrier to that flow. The South Pacific section of the Kuro-siwa is much less hampered by such impediments. That is quite a reason why the Gulf may be at a larger risk.

Now let's take a look at just how deep those cold currents are.

Very deep. This is a section across the Atlantic. To the left is the East coast with Florida, no mistake there. To the right are the Skandinavian peninsula, the UK, Spain and Africa. At the top is Greenland.

Beginning to have an idea of how the Gulf works? Great. Now take a closer look at where the sinking of cold water takes place? These points are called the Atlantic overturning points. The significant portion (the left part) of the Gulf sinks just off the coast at West Greenland. And what makes it possible? Salty water that is heavier than freshwater.

That is the same area where very significant build-up of fresh water reserves has been detected. Source? Melting Greenland freshwater ice sheets - there could be other reasons, but this is most compelling to consider. Important back-flowing section (the sinking part) of the Gulf is being bombarded by freshwater bombs breaking up the sinking stream into yet smaller streams. Coincidentally, the Gulf has been weakened. It has already slowed down about 30%.

This means that more and more of its activity is in the inner circle that just circulates warm water and air between the East Coast and Africa. Here, coastal surface water now often reaches an unbelievable 35 degrees centigrade. And when it does, it serves a perfect brewing ground for large and fast tornadoes.